federal prosecutors may file terrorism charges today against dzhokhar tsarnaev, the 19-year-old man accused of the boston marathon bombings. tsarnaev is under guard in serious but stable condition at a boston hospital with a gunshot wound to the neck. some investigators believe that wound may be the result of a suicide attempt before his arrest. he's now being questioned, but only for brief periods because of his medical condition and is responding mostly in writing because of the injury. investigators have been trying to piece together the events that led to the standoff between tsarnaev and police friday night after he was discovered by a watertown resident in a boat kept in his backyard. video from police helicopters show how he was arrested. an armored vehicle with a robotic arm lifted a tarp covering the boat. agents threw flash bang grenades to make sure there were no explosives. moments later, he was taken into custody. the rivere police department just released this picture of the police chief clearing the boat moments after he was apprehe apprehended. this morning boston police com